Generally, a compressor used in an air conditioning system for vehicles sucks refrigerant that has been evaporated by an evaporator, converts it into a high-temperature and high-pressure state, which can be easily liquefied, and then transfers it to a condenser. The compressor is configured to substantially compress refrigerant. Such compressors are classified into a reciprocating compressor which performs reciprocating motion to compress refrigerant, and a rotary compressor which performs rotational motion to compress refrigerant. Rotary compressors are classified into a mechanical type which rotates using an engine as a drive source, and an electric type which uses a motor as a drive source.
Electric compressors use an inverter to control the rotating speed thereof. The inverter employs a plurality of heat generating elements which generate heat during an operation process. Because such heat generating elements typically have low durability, there is a problem in that it is relatively difficult to cool the elements in such a way that refrigerant flows directly through the elements.
To overcome the foregoing problem, a technique was proposed, in which the installation location of an inverter is adjusted to an intake-side plate of a compressor so that heat generated from the inverter can be transferred to the intake-side plate and cooled by heat exchange with refrigerant flowing along the intake-side plate.
Such a conventional inverter installed in an electric compressor is used to control the operation of an air conditioning system for vehicles.
The inverter is configured with a typical motor drive circuit and a control unit. The motor drive circuit may be heated to high temperatures by heat generated from a semiconductor switching element, etc. constituting the circuit. In this case, a current control value for the semiconductor element in the inverter is reduced by high-temperature heat. If current higher than the control value is applied, the semiconductor element may be damaged. Furthermore, since the electric compressor is disposed in an engine room, the inverter may be maintained in a high-temperature state by heat generated from an engine.
To minimize heat of the heat generating element installed in the inverter, a conventional technique in which thermal grease is applied to a lower surface of a separate support body enclosing a lower portion of the heat generating element so as to reduce heat of the heat generating element which is operated at high temperatures, was proposed. However, there is a problem in that because the thickness of the support body is added to the thickness of the intake-side plate of the compressor, heat exchange between low-temperature refrigerant and the heat generating device cannot be reliably performed.
The above-mentioned problem causes malfunction due to overheating of the heat generating device. Moreover, the addition of the separate support body increases the production cost. Therefore, countermeasures for solving the problems are required.